Definition of four-stroke in English:

adjective

Unlike two-stroke engines that have simple openings or ports for intake and exhaust, four-stroke engines have intake and exhaust valves at each cylinder head.

The combustion chamber of a four-stroke engine is designed to induce turbulence through the addition of ‘squish’ areas in which the top of the piston is the mirror image of a corresponding area of the cylinder head.

In four-stroke engines, one of the strokes is called the compression stroke.